1. Field of the Invention
The present invention relates to a method for molding a polypropylene resin. More particularly, the present invention relates to a method for molding a foamed article of a polypropylene resin having good appearance.
2. Description of the Related Art
For the production of a foamed article of a thermoplastic resin, injection molding methods have been proposed (see Japanese Patent Publication No. 22213/1964 and Japanese Patent Kokai Publication No. 24913/1985).
However, the above conventional processes have some drawbacks as follows:
In the method disclosed in Japanese Patent Publication No. 22213/1964, a foaming condition in a step for supplying a resin melt in a mold cavity is insufficiently controlled. Then, in some cases, a part of the resin is already foamed in the resin supplying step so that it is difficult to produce stably a molded article having no flash or silver mark on an article surface. In the method disclosed in Japanese Patent Kokai Publication No. 24913/1985, an apparatus for injecting a fluid or gas into a resin melt for foaming and a position of foaming of an article is largely limited by a position of an inlet for the liquid or gas.